Well, that is a baited question. Meaning all the alligators out there will take a bite out of me if I answer incorrectly. So here is how I inspect it. It is a visual inspection. There is no tool to use for inspection. You know that. However, I have seen thousands of seats in my lifetime. It is difficult to determine the 60 and I know that many are doing 70. As for the 30 and 45, I have not seen anyone manipulating those angles. If I find seats that are butchered I have three valves cut to 30,45,60. I also have the machinist red dye. If need be I will start lapping. I guarantee that if I say it is out of spec, it is out of spec.